Medical marijuana just might cause a small drop in crime

But results say nothing about general legalization.

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There has been a general trend toward decriminalizing marijuana in the US, one that was spearheaded by the legalization of its use in medical situations. Those efforts have been opposed by many who argue that easy access to pot will lead people into harder drugs and boost the rate of unrelated crimes.

Although it's too soon to tell what might come from some of the more recent efforts—like full legalization or making possession a misdemeanor—medical marijuana laws have been on the books for long enough that it's possible to do some analysis on the results. Some researchers at the University of Texas-Dallas' Program in Criminology have done just that. They have found that medical marijuana laws aren't associated with an increase in crime, and they may even trigger a slight decrease in homicide and assault.

The challenge with these studies is to figure out which sociological and demographic factors are likely to also influence crime rates. These authors took about a dozen factors into account, including things like beer consumption and the percentage of the population with college degrees. Even before those were considered, crime rates appeared to be dropping faster in states that allowed medical usage; once the extraneous factors were taken into account, crime in general clearly dropped, and homicide and assault both showed statistically significant declines.

How could this possibly happen? The authors suggest that the clinics and growing facilities will typically put security measures in place, and some of those (like watchmen and closed-circuit cameras) could have an effect on the surrounding neighborhood. They would also counteract the crime that seems most likely to increase once these facilities are opened: burglary by those attracted to either the cash on hand or the goods being traded. (Contrary to some expectations, burglaries didn't increase in states that allowed medical marijuana.)

The study is quire preliminary, and there seems to be a number of other demographic factors that could have been included in the analysis but weren't. And it will still take a few years before we'll be able to look at the impact of other aspects of the decriminalization effort.